![]() As in the 1D model the IAW is not enveloped in time, which allows a proper treatment of strongly-coupled SBS, while the electron plasma wave is spatially and temporally enveloped. The Raman light frequency is downshifted from the pump by the plasma frequency. Each light wave is described by a space envelope equation under the paraxial approximation. The pump laser light is coupled both to Brillouin and Raman backscattered or amplified light. 22,23 This code contains a number of extra features with respect to the envelope model described above, in addition to allowing a full 3D description. To justify this statement we have performed a systematic comparison of the solution of the coupled equations above with 2D and 3D simulations performed with pF3D. Even if they are limited to a 1D description (along the direction of propagation of the laser pulses in a counter-propagative geometry), the estimate that can be derived and their full numerical resolution turns out to be very effective in describing the interaction process in a realistic configuration. II prove to be a very powerful tool for understanding the sc-SBS regime and for proposing schemes that allow the manipulation of intense laser pulses. ![]() The intensity of the first peak becomes very high, while the pulse gets compressed. During this stage the phase of the density varies very little, while the seed, the pump, and the global phase all vary significantly, creating a sort of wave train. When the energy transfer is such that the intensity of the seed becomes comparable to the pump intensity, the system enters the so-called self-similar regime. 8 During the exponential stage the phase of the pump is still basically unchanged. The estimated time for the seed phase to reach this value is γ sc t i = 1.7, or more accurately γ sc t i = 2.2 if one takes (correctly) into account the convective terms. Combined with the total phase expression one obtains the phase of the seed when it enters the exponential stage: φ s = 2/5 π. ( 3) and ( 4), we know that the total phase is almost constant: ϑ = −4 π/3. Then E s ∝ e γ s c t, N ∝ e γ s c t while φ s = φ s 0 + γ s c / 3 t, φ = φ 0 − γ s c / 3 t. ![]() We write E s = E s e i ω s c * t, N = N e − i ω s c t, and ω s c = ω ̃ s c + i γ s c. In order to obtain a well-defined and “clean” effect on the coherent light, the modification time is given by either the characteristic pulse length or the plasma self-modification time (e.g., wave-breaking of a regular structure).Īfter the initial stage, both the seed and the ion wave grow exponentially. Plasma optics is therefore a transient or dynamical optical element, driven by the finite pulse length of the laser beam. As the laser modification is induced by the laser itself, the interaction is limited in time, and it does not substantially modify the initial plasma equilibrium. This makes it particularly interesting for high-intensity laser pulses. Due to the fact that in a plasma matter is already broken down, it can sustain much higher fluences than standard optical materials. However, it differs in two fundamental ways. A plasma can therefore be used in the same way as standard solid-state based optical materials. Plasma optics exploits the fact that a laser interacting with a fully-ionized plasma is subject to feedback from the plasma itself, affecting its propagation and properties. A scheme that exploits this coupling in order to use the plasma as a wave plate is also suggested. The understanding of the phase evolution allows control of the directionality of the energy transfer via the phase relation between the pulses. This includes the role of the global phase in the spatio-temporal evolution of the three-wave coupled equations for backscattering that allows a description of the coupling dynamics and the various stages of amplification from the initial growth to the so-called self-similar regime. The strong-coupling regime of Brillouin scattering (sc-SBS) is of particular interest: recent progress in this domain is presented here. Plasmas can directly amplify or alter the characteristics of ultra-short laser pulses via the three-wave coupling equations for parametric processes. The use of plasmas provides a way to overcome the low damage threshold of classical solid-state based optical materials, which is the main limitation encountered in producing and manipulating intense and energetic laser pulses.
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